JP2000025413A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide novel cushion rubber. SOLUTION: This pneumatic tire consists of a toroid-shaped carcass 6, belt layers 7 positioned on the outer side in the tire radius direction of the carcass 6, a cushion rubber 9 extended along the carcass 6 between the outer side in the tire axial direction 7e of the belt layers 7 and the carcass 6. The cushion rubber 9 is constituted by a three-layer structure consisting of an inner layer rubber 10 on the side of the carcass 6, an outer layer rubber 12 on the side of the belt layers 7, an intermediate layer 11 held between the inner layer rubber 10 and the outer layer rubber 12. The inner layer rubber 10 and the outer layer rubber 12, which are integrated at an inner end (i) and an outer end (o) in the tire axial direction, are formed by a rubber component mainly made of natural rubber. In addition, the intermediate layer rubber 11 is formed by a rubber component having not less than 1% difference in polymer ratio or carbon ratio from that of the inner layer rubber 10 and the outer layer rubber 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having an improved cushion rubber.

[0002]

2. Description of the Related Art A heavy duty radial tire used for a light truck, a heavy truck or a bus, for example, is shown in FIG.
As shown in the figure, a toroidal carcass a made of, for example, a steel cord forming a tire skeleton, and a belt layer c in which, for example, metal cords and the like are arranged inside the tread portion b and outside the carcass a in the tire radial direction. It has. The belt edge e, which is the outer side portion of the belt layer c in the tire axial direction, terminates at a position separated from the carcass a due to a difference in curvature, and is liable to be repeatedly deformed by rolling of the tire.

Conventionally, a cushion rubber d is extended between the belt edge e and the carcass a along the carcass a to reduce the impact or distortion of the belt edge e, and to reduce the cord looseness and the like. Separation is prevented.

A conventional cushion rubber d is, for example, an inner rubber d having a relatively small thickness disposed on the carcass a side.
1 and an outer rubber layer d disposed outside thereof and having a relatively large thickness.
In many cases, it is composed of two.

The inner layer rubber d1 contains a rubber component mainly composed of natural rubber and a large amount of a tackifier such as an adhesive resin in order to improve the adhesive property in order to improve the sticking property to the carcass a in the molding process. Rubber is adopted. On the other hand, the outer rubber d2, which constitutes the majority of the cushion rubber, is most required to have elongation performance due to deformation. However, the sidewall rubber f, which is appropriately bonded to the outer rubber d2,
It is also necessary to improve the adhesion to the base tread rubber g, the cap tread rubber h, and the like. Therefore, the outer rubber d2 also needs to be compounded with a tackifier in the same manner as the inner rubber d1, and the total compounding amount of the tackifier is large, causing an increase in tire cost.

The present invention has been devised in view of the above situation. In particular, according to the first and second aspects of the present invention, the cushion rubber d includes an inner layer rubber on the carcass side, an outer layer rubber on the belt layer side, and It is composed of a three-layer structure of an intermediate layer rubber sandwiched between an inner layer rubber and an outer layer rubber. The intermediate layer rubber is formed of a rubber composition having a polymer ratio or a carbon ratio different from the outer layer rubber by 1% or more from the inner layer rubber. On the basis of this, it is an object of the present invention to provide a pneumatic tire that can reduce, for example, an adhesive and a tackifier in an intermediate layer rubber without deteriorating the adhesive performance, thereby helping to reduce costs.

[0007]

The first object of the present invention is as follows.
The described invention is a pneumatic tire comprising a carcass extending from a tread portion to a bead core of a bead portion via a sidewall portion, and a belt layer disposed radially outward of the carcass and inward of the tread portion. The cushion rubber extending along the carcass between the tire layer axial direction outer portion of the belt layer and the carcass is a carcass side inner layer rubber, a belt layer side outer layer rubber, and an inner layer rubber and an outer layer rubber. The inner rubber and the outer rubber are integrated at the inner end and the outer end of the cushion rubber in the tire axial direction,
The inner rubber and the outer rubber are formed from a rubber composition mainly composed of natural rubber, and the intermediate rubber is formed from a rubber composition having a polymer ratio or a carbon ratio different from the inner rubber and the outer rubber by 1% or more. Features.

The invention according to claim 2 is characterized in that the inner rubber and the outer rubber are made of the same rubber composition having a difference in polymer ratio or carbon ratio of less than 1%. It is a pneumatic tire.

The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the intermediate layer rubber does not contain a tackifier as an additive.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a toroidal carcass 6 is engaged with a bead core (not shown) from a tread portion 2 through a sidewall portion 3, and is disposed radially outside the carcass 6 and inside the tread portion 2. 1 shows a heavy-duty radial tire provided with a belt layer 7.

The carcass 6 is composed of one or more carcass plies 6A in which carcass cords are arranged at an angle of 75 ° to 90 ° with respect to the tire equator C, in this embodiment, one carcass ply 6A. As the carcass cord, a metal cord having high rigidity is employed in the present embodiment.

The belt layer 7 is composed of two or more, in this embodiment, three belt plies 7A, 7B, 7C in which belt cords are arranged at an angle to the tire equator C. In this example, a metal cord is employed as the belt cord.

A cushion rubber 9 is arranged between the carcass 6 and the outer portion 7 e of the belt layer 7 in the tire axial direction so as to extend along the carcass 6.
The cushion rubber 9 includes an inner layer rubber 10 on the carcass 6 side.
And an outer rubber layer 12 on the side of the belt layer 7, and an intermediate rubber layer 11 sandwiched between the inner rubber layer 10 and the outer rubber layer 12.

The inner rubber 10 and the outer rubber 12 are integrated at the inner end i and the outer end o of the cushion rubber 9 in the tire axial direction so as to surround the intermediate rubber 11. The inner rubber layer 10 and the outer rubber layer 12 are illustrated as having a smaller thickness than the intermediate rubber layer 11. Further, the inner rubber layer 10 and the outer rubber layer 12 are formed of a rubber composition mainly composed of natural rubber, and the intermediate rubber layer 11 is formed of a rubber composition having a compounding difference from the inner rubber layer 10 or the outer rubber layer 12. Has formed.

As described above, the inner rubber 10 disposed on the carcass 6 side and the outer rubber 12 disposed on the belt layer 7 side are made of a rubber composition mainly composed of natural rubber, so that the surrounding ply is formed. The adhesiveness or adhesion to rubber or rubber can be improved, the sticking property during tire molding can be improved, and delamination of rubber can be suitably prevented.

In this embodiment, the inner rubber 10 and the outer rubber 12 are made of the same rubber composition mainly composed of natural rubber. In this case, the cushion rubber 9 can be configured as a three-layer structure while suppressing the rubber composition to two types, that is, the rubber composition of the inner and outer rubber layers 10 and 11 and the rubber composition of the intermediate rubber layer 12.

The rubber composition of the inner and outer rubber layers 10 and 11 preferably contains at least 90 parts by weight, more preferably at least 95 parts by weight of natural rubber per 100 parts by weight of the rubber component. Then, it is desirable that appropriate hardness and tackiness are imparted by appropriately blending carbon black, a tackifier and the like with such a rubber component.

On the other hand, since the intermediate rubber 11 is wrapped in the inner rubber 10 and the outer rubber 12 having high adhesiveness, it is not necessary to increase its own adhesiveness.
Alternatively, a rubber having a difference in composition from the outer rubber 12 can be used.

In the present invention, the inner rubber 10 and the outer rubber 12
Is defined as a difference between the polymer ratio and the carbon ratio by 1% or more. The value of 1% or more is a value equal to or higher than the rubber analysis accuracy, but it is preferable that there is a difference of 2% or more. In other words, those having a difference between the polymer ratio and the carbon ratio of less than 1% are treated as the same rubber in the compounding.

Therefore, various rubbers such as a rubber having a high ability to alleviate the strain accompanying the rolling of the tire, a rubber having an excellent elongation characteristic, and a rubber having a low cost can be used as the intermediate layer rubber 11. There is an advantage that the degree of freedom in selecting rubber is increased. In the present example, the intermediate layer rubber 1 contains a rubber component 100
70 to 85 parts by weight of a natural rubber and 30 to 15 parts by weight of a styrene-butadiene rubber,
F-carbon is 40 to 50 parts by weight, further comprising a rubber composition excellent in elongation blended with oil and the like, if necessary,
The example does not include a tackifier or a tackifier.
Thereby, the total compounding amount of the tackifier of the cushion rubber 9 can be greatly reduced, which is useful for reducing the cost of the tire.

The inner rubber 10 and the outer rubber 12 are integrated at the inner end i and the outer end o of the cushion rubber 9 in the tire radial direction, so that the inner rubber 10 and the outer rubber 12 having high adhesive performance are provided. However, since the intermediate layer rubber 11 is firmly wrapped, the mutual bonding force is strong, and delamination can be effectively prevented.

The inner rubber 10 of the cushion rubber 9
As a mode in which the outer rubber layer 12 is integrated at the inner end portion i and the outer end portion o in the tire radial direction, as shown in FIG. The inner rubber layer 10 and the outer rubber layer 12 are wrapped around the intermediate rubber layer 11 and extruded and formed as a single unit. Alternatively, as shown in FIG. 3, the rubber of each layer is extruded from three bases of an extruder. The cushion rubber 9 can be formed by other various methods. In addition, inner layer rubber 10,
The intermediate layer rubber 11 and the outer layer rubber 12 may be individually extruded and formed into a strip shape, and may be sequentially attached to the carcass 6 without being integrated before molding.

Although the embodiment of the present invention has been described by taking a heavy load radial tire as an example, the present invention can also be applied to a passenger car tire, an aircraft tire, and the like. Further, the intermediate layer rubber 11 is not limited to the exemplified composition, and it is of course possible to use another composition.

[0024]

EXAMPLES Table 1 shows the composition of the outer rubber and the inner rubber (both have the same composition).

[0025]

[Table 1]

Next, the intermediate layer rubber was blended as shown in Table 2 (Examples 1 and 2 each had a difference of 1% or more in polymer ratio from the outer layer and the inner layer rubber). A prototype tire was manufactured and its performance was evaluated for durability, adhesive strength, and cost. Tires having cushion rubber having the structure shown in FIG. 4 (Comparative Examples 1 and 2) were also prototyped, and the performance was compared.

With respect to the durability performance, a load 1.4 times the maximum load specified in JIS was applied, the vehicle was run on the drum at a speed of 70 km / H, and 10 km every 2 hours.
The running time until the tire was broken was determined by increasing the speed by / H, and the running time was indicated by an index with Comparative Example 2 being 100.

With respect to the adhesive strength, after forming the raw cover, the raw cover was allowed to stand at a constant temperature for 4 hours, and the state of floating from the inner surface of the raw cover due to poor adhesion was confirmed.

The cost of Comparative Example 2 was 100
It was indicated by an index. The higher the value, the better. Table 2 shows the test results.

[0030]

[Table 2]

As a result of the test, it was confirmed that the tires of the examples maintain the adhesive force without substantially impairing the durability performance and can reduce the cost.

[0032]

As described above, according to the first aspect of the present invention, the inner layer rubber on the carcass side and the outer layer rubber on the belt layer side are made of a rubber composition mainly composed of natural rubber, so that the inner layer rubber is formed. Adhesive performance between the carcass with rubber and the belt layer or sidewall rubber with the outer rubber can be maintained. For this reason, various rubber compositions can be suitably adopted as the intermediate layer rubber regardless of increasing the adhesive strength, which helps to reduce the cost.

By integrating the inner rubber and the outer rubber at the inner and outer ends of the cushion rubber in the radial direction of the tire, the bonding between the inner rubber, the intermediate rubber and the outer rubber is strengthened. Delamination of each rubber can be effectively prevented.

According to the second aspect of the present invention, since the inner rubber and the outer rubber are made of the same rubber composition mainly composed of natural rubber, a sidewall rubber having a three-layer structure can be manufactured with two kinds of rubbers. And productivity can be improved.

According to the third aspect of the present invention, since the intermediate rubber does not contain a tackifier, the amount of the tackifier in the cushion rubber can be reduced.
Helps further reduce costs.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a tire showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an example of a cushion rubber before tire attachment.

FIG. 3 is a sectional view showing another example of the cushion rubber before the tire is attached.

FIG. 4 is a partial sectional view of a tire showing a conventional cushion rubber.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 9 Cushion rubber 10 Inner layer rubber 11 Intermediate layer rubber 12 Outer layer rubber

Claims (3)

[Claims] 1. A pneumatic tire comprising a carcass extending from a tread portion to a bead core of a bead portion via a sidewall portion, and a belt layer disposed radially outward of the carcass and inward of the tread portion. The cushion rubber extending along the carcass between the tire axial direction outer portion of the belt layer and the carcass includes an inner rubber layer on the carcass side, an outer rubber layer on the belt layer side, and an inner rubber layer and an outer rubber layer. The rubber layer is composed of a three-layer structure with an intermediate rubber layer sandwiched between the rubber layers, and the inner rubber layer and the outer rubber layer are integrated at the inner and outer ends of the cushion rubber in the tire axial direction. Is formed of a rubber composition mainly composed of natural rubber, and the intermediate layer rubber is formed of a rubber composition having a polymer ratio or a carbon ratio different from the outer layer rubber by 1% or more from the inner layer rubber. Pneumatic tire, characterized in that it was. 2. The pneumatic tire according to claim 1, wherein the inner rubber and the outer rubber are made of the same rubber composition having a difference in polymer ratio or carbon ratio of less than 1%. 3. The pneumatic tire according to claim 1, wherein the intermediate layer rubber does not contain a tackifier as an additive.